The aim of this file is to serve as a guide for the developers, to aid us to
get clean and uniform code. This document is still incomplete.
-We really like to have new developers joining the LyX Project. However
-since we have had problems in the past with developers leaving the
+We really like to have new developers joining the LyX Project. However,
+we have had problems in the past with developers leaving the
project and their contributed code in a far from perfect state. Most
-of this happened before that we really became aware of these issues,
+of this happened before we really became aware of these issues,
but still, we don't want it to happen again. So we have put together
some guidelines and rules for the developers.
General
-------
-These guidelines should save us a lot of work while cleaning up the code and
-help us to have quality code. LyX has been haunted by problems coming from
-unfinished projects by people who have left the team. Those problems will
+These guidelines should save us a lot of work while cleaning up the code and
+help us to have quality code. LyX has been haunted by problems coming from
+unfinished projects by people who have left the team. Those problems will
hopefully disappear if the code is easy to hand over to somebody else.
-In general, if you want to contribute to the main source, we expect at least
+In general, if you want to contribute to the main source, we expect at least
that you:
- the most important rule first: kiss (keep it simple stupid), always
use a simple implementation in favor of a more complicated one.
This eases maintenance a lot.
-- write good C++ code: Readable, well commented and taking advantage of the
+- write good C++ code: Readable, well commented and taking advantage of the
OO model. Follow the formatting guidelines. See Formatting.
-- adapt the code to the structures already existing in LyX, or in case that
- you have better ideas, discuss them on the developer's list before writing
- the code.
+- adapt the code to the structures already existing in LyX, or in the case
+ that you have better ideas, discuss them on the developer's list before
+ writing the code.
- take advantage of the C++ standard library. especially don't use
- custom containers when a standard container is usable, learn to use
+ custom containers when a standard container is usable; learn to use
the algorithms and functors in the standard library.
- be aware of exceptions and write exception safe code. See Exceptions.
- document all variables, methods, functions, classes etc. We are
- using the source documentation program doc++, a program that handles
- javadoc syntax, to document sources. See Source Documentation.
+ using the source documentation program doxygen, a program that handles
+ javadoc syntax, to document sources. You can download doxygen from :
+
+ http://www.stack.nl/~dimitri/doxygen/
+
- we have certain code constructs that we try to follow. See Code
Constructs.
---------------
It is implicitly understood that all patches contributed to The LyX
-Project is under the Gnu General Public License, it you have a problem
-with that, don't contribute code.
+Project is under the Gnu General Public License, version 2 or later.
+If you have a problem with that, don't contribute code.
-Also please don't just pup up out of the blue with a huge patch (or
+Also please don't just pop up out of the blue with a huge patch (or
small) that changes something substantial in LyX. Always discuss your
-ideas with the developers on the developers mailing list.
+ideas with the developers on the developer's mailing list.
When you create the patch, please use "diff -up" since we find that a
lot easier to read than the other diff formats. Also please do not
-send patches that implements/fix several different things, several
+send patches that implements or fixes several different things; several
patches is a much better option.
-We also expect you to provide a ChangeLog entry with every patch, this
+We also require you to provide a ChangeLog entry with every patch, this
describes shortly what the patch is doing. The ChangeLog entry follows
this syntax:
* src/support/lyxstring.C (find): assert bug fixed.
+Note that there are specific ChangeLogs for most directories; use those
+rather than the top-level one.
Code Constructs
---------------
-We have several guidelines on code constructs, some of these exists to
+We have several guidelines on code constructs, some of these exist to
make the code faster, others to make the code clearer. Yet others
-exists to make us able to take advantage of the strong type checking
+exist to allow us to take advantage of the strong type checking
in C++.
-
+
- Declaration of variables should wait as long as possible. The rule
is: "Don't declare it until you need it." In C++ there are a lot of
user defined types, and these can very often be expensive to
initialize. This rule connects to the next rule too.
+- declare the variable as const if you don't need to change it. This
+ applies to POD types like int as well as classes.
+
- Make the scope of a variable as small as possible.
+- Make good use of namespaces. Prefer anonymous namespaces to declaring
+ "static" for file scope.
+
- Prefer preincrement to postincrement whenever possible.
Preincrement has potential of being faster than postincrement. Just
- thing about the obvious implementations of pre/post-increment. This
+ think about the obvious implementations of pre/post-increment. This
rule applies to decrement too.
++T;
- Avoid using the default cases in switch statements unless you have
too. Use the correct type for the switch expression and let the
- compiler ensure that all cases are exhausted.
+ compiler ensure that all cases are exhausted.
enum Foo {
foo,
Even if LyX currently is not using exceptions we need to be aware of
them. One important thing to realize is that you often do not have to
-use throw,try or catch to be exception safe. Let's look at the
+use throw, try or catch to be exception safe. Let's look at the
different types of exceptions safety: (These are taken from Herb
-Sutters book[ExC++]
+Sutter's book[ExC++]
"
1. Basic guarantee: Even in the presence of exceptions thrown by T or
other exceptions, Stack objects don't leak resources.
Note that this also implies that the container will be
- destructible and usable even if an exception is thrown wile
+ destructible and usable even if an exception is thrown while
performing some container operation. However, if an exception
is thrown, the container will be in a consistent, but not
necessarily predictable, state. Containers that support the
client calls Top and then attempts a Push that fails because
of an exception, then the state of the Stack object must be
unchanged and the reference returned from the prior call to
- Top must still be valid. For more information on there
+ Top must still be valid. For more information on these
guarantees, see Dave Abrahams's documentation of the SGI
exception-safe standard library adaption at:
- http://www.metabyte.com/~fbp/stl/eg_contract.html
+
+ http://www.stlport.org/doc/exception_safety.html
Probably the most interesting point here is that when you
implement the basic guarantee, the strong guarantee often
In addition to these two guarantees, there is one more
guarantee that certain functions must provide in order to make
- overall exception safety possible:
+ overall exception safety possible:
3. Nothrow guarantee: The function will not emit an exception under any
circumstances.
functions are guaranteed not to throw. In particular, we've
seen that this is true for destructors; later in this
miniseries, we'll see that it's also needed in certain helper
- functions, such as Swap().
+ functions, such as Swap().
"
For all cases where we might be able to write exception safe functions
without using try, throw or catch we should do so. In particular we
should look over all destructors to ensure that they are as exception
-safe at possible.
+safe as possible.
Later when more compiler support exceptions sufficiently well we will
begin using them too. One reason for this is that the C++ standard
};
-NOT-
enum { one = 1, two = 2, three 3 }; // wrong
+ -NOT-
+ enum {
+ ONE = 1,
+ TWO = 2,
+ THREE = 3
+ };
* Naming rules for classes
[I am not so sure about the LyX prefix]
- Class names are usually capitalized, and function names lowercased.
- Enums are named like Classes, enum values in CAPS.
+ Enums are named like Classes, values are usually in lower-case.
- Long variables are named like thisLongVariableName.
* Formatting
- - Please adapt the formatting of your code to the setting in LyX in that
- particular file. Lars and Asger are slowly, but surely moving the source
- towards Linux kernel style formatting, aka K&R style. We suggest that you
- also do this, but this is NOT something that has been decided generally.
-
+ - Adapt the formatting of your code to the one used in the
+ other parts of LyX. In case there is different formatting for
+ the same construct, use the one used more often.
* Use existing structures
* Declarations
-
+
- Use this order for the access sections of your class: public,
protected, private. The public section is interesting for every
user of the class. The private section is only of interest for the
implementors of the class (you). [Obviously not true since this is
for developers, and we do not want one developer only to be able to
read and understand the implementation of class internals. Lgb]
-
- - Avoid to declare global objects in the declaration file of the class.
- If the same variable is used for all object, use a static member.
- - Avoid global or static variables. An exception to this rule is
+ - Avoid declaring global objects in the declaration file of the class.
+ If the same variable is used for all objects, use a static member.
+
+ - Avoid global or static variables. An exception to this rule is
very private stuff like the math stack.
- - Use the const keyword like this: char const * instead of const char *
- because this is more logical.
+* File headers
+
+ - If you create a new file, the top of the file should look something
+ like this :
+
+ /**
+ * \file NewFile.C
+ * This file is part of LyX, the document processor.
+ * Licence details can be found in the file COPYING.
+ *
+ * \author Kaiser Sose
+ *
+ * Full author contact details are available in file CREDITS
+ */
* Documentation
- You should document what the function does, not the implementation.
- in the .C files you document the implementation.
- Single line description (///), multiple lines description (/** ... */)
- - You make the documentation by doing "make srcdoc" in the root,
- and then you'll find HTML in the srcdoc/ directory. Read with
- Netscape for best results.
+ - see the doxygen webpage referenced above
* NAMING RULES FOR USER-COMMANDS
-
+
Here's the set of rules to apply when a new command name is introduced:
-
- 1) Use the object.event order. That is, use `word-forward' instead of
+
+ 1) Use the object.event order. That is, use `word-forward' instead of
`forward-word'.
2) Don't introduce an alias for an already named object. Same for events.
3) Forward movement or focus is called `forward' (not `right').
8) The end of an object is called `end'.
-* Using external GUI constructors (XForms fdesign)
-
- - Fdesign generated files should not be changed at all. The only changes
- needed are gettext, compability with 0.88 or when you have made your own
- xforms objects and have just a dummy in the .fd file in place of your
- own. In case you have to change the generated files for any of the
- reasons above, you should provide a patch against the clean generated
- file. Your callbacks must be in a separate file.
-
*************************************************************
How to create class interfaces.
(a.k.a How Non-Member Functions Improve Encapsulation)
======================================================
- I recently read an article by Scott Meyers in C/C++ Users
+ I recently read an article by Scott Meyers in C/C++ User's
Journal (Vol.18,No.2), where he makes a strong case on how non-member
-functions makes classes more encapsulated, not less. Just to skipping
+functions makes classes more encapsulated, not less. Just skipping
to the core of this provides us with the following algorithm for
deciding what kind of function to add to a class interface:
make f a non-member function;
else
make f a member function of C;
-
-Unfortunately, to make the best use of this kind of Class API's we
-need namespaces. As soon as Jean-Marc stops using gcc 2.8 and other
-compilers seem more or less up to date on namespaces we will begin to
-use them. _BUT_ we should begin to use the above algoritm ASAP. We
-should also go through old code and apply this algorithm to the
-existing member functions. That will help maintainability in the
-future.
(I'll fill in more from Scott Meyers article when time allows.)
projects / lyx.git / blobdiff